Hydrogenation and cracking of oils



4 p 1937. R. H. McKEE 2,093,843

HYDROGENATION AND CRA CK I ENG OF OILS Filed Nov. 7, 1955 R0 11; M ee atente opt. 2i,

Ralph E. McKee, New York, N. Y., assignor, by mesne assignments, to Ernest A. (icon, New

York, N. Y. 7

Application November '2, 1935, Serial No. 48,733

4 Claim (Cl. 196-62) This invention relates to the hydrogenation and cracking of oils and more particularly to an improved process of producing motor fuels, and especially gasoline of high quality, from oils, preferably oils from which such fuels cannot readily be obtained in commercial percentages by fractional distillation.

The present. application is'a continuation-inpart of my copending application Serial No. 486,857, filed October 6, 1930.

Due primarily to the increasing consumption of motor fuels, such as gasoline, many attempts have been made to devise suitable processes for producing motor fuels from petroleum from which gasoline and kerosene have been distilled and other materials from which such motor fuels are not directly obtainable, as by fractional distillation. One of such processes is commonly known as berginization, developed from the pioneer work of Friedrich Bergius. In the early process practiced by Bergius, powdered coal, either alone or, as was found preferable, suspended in an oil vehicle whereby the product assumes the form of a paste, was'subjected to the simultaneous action of' heat and hydrogen under a high pressure, say a temperature of around 500 C. (932 F.), and a pressure of at least 300 pounds per square inch of hydrogen gas. In later developmentsof the process a pressure of from 1500 to 2500 pounds has been employed. Under these conditions the bituminous coal was hydrogenated and the resulting heavy oil partially cracked to give a percentage of products useful as motor fuel.

In the later developed process knownas berginization for the production of motor fuels, crude petroleum from which the gasoline and kerosene have been distilled is treated in a manner similar to the original process, whereby two processes take place simultaneously, the process of-hydrogenation and the process of cracking, and there results a considerable percentage, say 35 per cent., of gasoline composed largely of saturated hydrocarbons. This process is known in the industry as destructive hydrogenation.

While the last referred to method has met with some degree of commercial success, there are several handicaps to the process. In the first place, the gasoline obtained is not of the character commonly desired due to the fact that it is composed largely of saturated hydrocarbons and hence will knock strongly in an automobile engine} Another disadvantage of the process is that the amount of hydrogen used is excessively produced by cracking and so becomes an important item in the expense of operation. Furthermore, the process requires considerable time and accordingly is operated most efliciently as a batch process rather than as a continuous process. Also, actual tests have demonstrated that there is a substantial formation of asphaltic material and coke-another undesirable factor of the process. Moreover, it has been found that during the process considerable amounts of other gases such as methane, ethylene and the like are formed and dilute the hydrogen. When this diluting material passes a percentage of about 20 per cent., the hydrogenation becomes quite inefficient. This formation of undesirable gases constitutes an additional handicap because of the fact that the exit gases, although rich in hydrogen, are diflicult to rework cheaply to recover the hydrogen in approximately pure condition. A further disadvantage resulting from this simultaneous hydrogenation and cracking process is found in the requirement for a considerable addition of external heat in the operation. of the process. While hydrogenation of the oils evolves a substantial amount of heat, it is less than is absorbed in the cracking of the oils. Finally, the process has been found disadvantageous due to the impossibility of making practical use of hydrogenation catalysts. While such catalysts may be initially employed with some advantage, the coke and asphaltic material formed by the cracking quickly coatthe catalysts whereby their efliciency is reduced to a marked degree.

The present invention is designed to overcome the disadvantages set forth above and to provide for the production of motor fuels such as gasoline from residue oils and the like, a process which operates most advantageously as a continuous process, which produces an increased yield of product of exceptionally high quality, and which is sumciently economical in operation to be commercially practicable; The present invention takes into account th fact that petroleum materials have definite critical temperatures which canbe readily .deter-' mined by known methods. (See Critical temperatures and oil cracking by McKee and Parker, Industrial and EngineeringChemistry, vol. 20, p. 1169.) For example, a gasoline may have a critical temperature of 310 C. (590 F.), and a mixture of gasoline and kerosene may have a critical temperature of say 375 C, (707. F.), a gas oil 480 C. (899 F.) and so on. Similarly, the higher petroleum oils have definite critical temperatures which can be determined. The invention further takes into account the fact that when an oil is heated under pressure above its critical temperature it exhibits certain desired characteristics which it does not normally exhibit. For example, if asphalt or similar materials, which do not vaporize under ordinary conditions areadded to gasoline, they will be soluble to a certain extent in the gasoline above the critical temperature as well as in-the liquid gasoline, that is, they will be present in vapor condition in the gasoline vapor which is under pressure and above the critical temperature.

In the practice of the present process,.oils, such as a petroleum distillate or residue, are first hydrogenated and then, still as liquid, removed to another vessel in which they are heated to a higher temperature and cracked. The materials in the gas phase do not pass from the hydrogenation vessel to the cracking vessel. In the first;

or hydrogenation, vessel the temperature and pressure conditions are such that the temperature is below the critical temperature and ac,- cordingly a two phase reaction occurs with the liquid oil containing some dissolved hydrogen below and the hydrogen gas above. When the mixture has been heated to incipient hydrogenation the addition of more external heat is not necessary due to the evolution of heat resulting from the hydrogenation. This heat provided by the process itself is sufficient to carry the hydrogenation to completion.

In the cracking vessel, a temperature above a the critical temperature of the mixture of hydro- 100 atmospheres.

'that the critical temperature of the oil will be lowered by the presence of the dissolved hydro gen gas and this factor is to be taken into consideration. The temperatures employed in.the

second, or cracking, vessel will be of the order of 540 C. (1000 F.). Hydrogen gas is not purposefully introduced into the second vessel and the only hydrogen gas that will be present will be the small amount which is dissolved in the oil transferred from the hydrogenation vessel to the crackingvessel. Some hydrogen gas will be formed by the cracking process but the amount is insufficient to raise the partial pressure of hydrogen to give any substantial hydrogenation of the oil in thecracking vessel. Such hydrogenation is to be avoided because it would produce the undesired motor fuel of saturated type instead of the desired motor fuel of unsaturated and ring type (anti-knocking character).

In actual practice the process may be carried out in a variety of forms of apparatus. The apparatus will require pumps to pump the oil and hydrogen gas to give pressures of approximately I have found that the exact pressure is not important except as it influences the time required. With pressures lower than 100 atmospheres, say 40 atmospheres, a longer period of time is required and while pressures above 100 atmospheres may be employed to shorten the higher pressures, say 200 atmospheres.

through heated pipes of the type customarily.

employed in the continuous processes of oil cracking under high pressure. However, it is desirable to use pipes somewhat smaller than heretofore used in order to get the desired factor of safety in view of the higher pressures employed, 1500 pounds instead of 1000 pounds as previously used. After passing'the materiais through a heating coil formedof such pipes, the mixture of hydrogen gas and oil at a temperature below the critical temperature of the oil with its dissolved gas (which is lower, generally about 20 F. lower, than the critical temperature of the oil alone) is passed into a reaction vessel of suitable construction, preferably of cylindrical type. When such a cylindrical vessel is employed it is preferably set with its axis horizontal so that a maximum surfacecontact between the hydrogen gas and the liquid oil will be obtained. The hydrogenation of the oil is permitted to proceed in this reaction vessel.

In the accompanying drawing I have shown diagrammatically an assembly of apparatus suitable for use in the practice of my process.

Referring to the drawing, the oil to be treated As shown in the drawing, the pipe I2 connects with a hydrogenation apparatus l6 which has a valved gas outlet pipe II, a clean-out man-hole l8 and a valved liquid discharge pipe l9. Several return bends of the pipe 19 are arranged in a furnace 20 which is heated by a burner 2| and is provided with a. stack 22. The pipe l9 connects with a cracking unit 23 which isprovided with a clean-out man-hole 24 and a valved discharge pipe 25. The pipe 25 is connected with a separator 26 which is provided at the top thereof with a discharge pipe 21 which communicates with a crude motor oil condenser (not shown) and at the bottom thereof with a pipe 28 which communicates with a heavy oil storage container (not shown). Q

If desired, any conventional hydrogenation catalyst, such as nickel, alkali metal hydride or molybdenum sulfide, maybe employed in the hydrogenation vessel. This constitutes a distinct advantage over the process of berginization which, as stated above, has the handicap that any catalyst added to increase the rate of hydrogenation soon becomes covered with coke or asphaltic material formed by the simultaneous cracking and is thereby made inactive. Tests have demonstrated that this does not occur in the present process.

Following the hydrogenation of the oil in the hydrogenation vessel the oil, but not the gas, is then passed through a short coil .where it is heated to a desired cracking temperature, say about 540 C. (1000 F.) Under these conditions it is essentially, except for particles of coke or asphaltic materials present, above the critical temperature and is no longer in liquid condition, even though the pressure has not been reduced. The material is then passed into an insulated reaction chamber where, due to its own heat, cracking of the oil occurs. The process is a continuous one until, due to the cracking, the cracking vessel becomes so completely filled with coke that it requires emptying. The coke that is formed settles on the inner surface of the reaction chamber and acts as an insulator to prevent further loss ofheat.

aoeaeas No special stirring devices are necessary .either in the hydrogenation vessel or in the cracking vessel, which is a distinct advantage of the present process over the processes heretofore employed.

The mixtureof permanent gases obtained as lay-product from the cracking operation can be removed to obtain the'hydrogen needed for the hydrogenation step by any of several known processes.

Numerous raw materials may be treated according to the present process. For example, the process is'adapted for treating the residues from most crude petroleums which have been topped for gasoline and kerosene, or the residue left from a cracking process of the type commonly employed in this country, or shale oil, or the oils obtained from bituminous coal or lignites by socalled low temperature distillation, or the asphaltic oils obtained from tar sands, or the heavy crude petroleums.

In the actual practice of the process, the exact temperatures of treatment may be variously modoccurs at about 400 C. (750 F.). In the hydrogenation step, temperatures materially above 425 C. (800 F.) should not be employed since cracking then occurs with consequent coating of catalyst particles; In the cracking operation, the temperature is above the critical temperature and generally should be in the neighborhood of 540 C. (1000 F.) although satisfactory cracking often may be obtained at a somewhat lower temperature, but always under pressure.

The following specific example of the practice of the process may be considered as illustrative of the invention. Gas oil of a 300-350 C. (570- 660 F.) distillation range, such an oil having a critical temperature of about 480 C. (899 F.) at a pressure of 100 atmospheres of hydrogen was heated to a temperature of 425 C. (800 F.). A period of two hours was allowed for hydrogenation. During this treatment practically no cracking occurred (the particular gas oil treated obviously being one difficult to crack) and -there fore, of course, there was no formation of low boiling products useful as motor fuel. The hy-' drogenated oil, but not the gas phase, was then introduced into the cracking vessel, and the material heated to approximately 500 C. (932 F.) to

eifect cracking of the material. As a result of this treatment approximately 45 per cent. of the desired anti-knocking quality gasoline was ob- 90 tained.

As will be apparent from the foregoing, I have provided a process wherein a petroleum product is first hydrogenated and thereafter removed to another vessel in which the hydrogenated product is cracked. The initial treatment is, as pointed out 'above, simple hydrogenation and not a destructive hydrogenation of the type known as berginization. In the present process there is an absence or a minimum of cracking during the hydrogenation. There being no, cracking, the

products will not boil at a lower temperature be-.

cause the molecules are still approximately the same size as they were originally. The hydrogenated product, but not the gases above it, is re- 75 moved from the hydrogenation chamber and then of catalysts the same speed of hydrogenation subjected to higher temperatures for cracking in apparatus suitable for and intended only for the cracking operation. As a result of this treatment a commercially satisfactory yield of motor fuel of anti-knocking character is obtained from materials not in themselves suitable as motor fuels.

For the purpose of expediency the term petroleum is used in the subjolned claims in a broad sense to cover not only petroleum from wells, as the word is now commonly used, but also oils such as shale oil which formerly were covered by the word, and also oils which are similar to the oils now generally referred to as petroleums. Accordingly, for the purpose of the present application it will be understood that the term petroleum appearing in the claims is intended to include residue from crude petroleum which has been topped for gasoline and kerosene, the residue left from cracking processes of the types commonly employed in this country, shale oil, oils obtained from bituminous coal or lignites by socalled low temperature distillation, asphaltic oils obtained from tar sands, heavy crude petroleums tically no change of molecular size and hence no suitable as motor fuel which comprises subject' ing a liquid petroleum product containing com- Ponents relatively refractory to cracking to nondestructive hydrogenation at a temperature below approximately 800'F. and at superatmospheric pressure to hydrogenate said product with no substantial cracking thereof, separating materials present in the vapor phase from materials remaining in the liquid phase in the hydrogenation reaction, and cracking such liquid phase products in the absence of such vapor phase products to form motor fuel hydrocarbons.

2. A .process for producing motor fuel which comprises subjecting a higher boiling liquid petroleum product of unsaturated and polymerized character, such as residue oils from distillation and cracking operations, to nondestructive hydrogenation at a temperature below approximately 800 F. and at superatmospheric pressure to hydrogenate said product'with no substantial cracking thereof, separating materials present in gaseous phase from materials remaining in liquid phase during the hydrogenation operation, and cracking a portion of the hydrogenated liquid products, in the absence of said vapor phase products, under conditions of temperature and pressure to form vapors comprising fractions of gasoline boiling range having desired anti-knock properties.

3. A process of producing valuable products of gasoline boiling range and heavier products which comprises subjecting a higher boiling liquid petroleum product, such as residue oil resulting from topping crude petroleum, to nondestructive hydrogenation at a temperature below approximately 800 F. and at superatmospherlc pressure sufficient to maintain said product substantially in liquid phase during the operation to ,hydrogenate said product with no substantial cracking thereof, separating materials present in vapor phase from materials remaining in liquid phase during the hydrogenation operation, and crack- 1 0 ing the separated hydrogenated products remaining in, liquid phase to form motor fuel products of gasoline boiling range and heavier products.

4. A process for producing motor fuel which comprises subjecting a liquid petroleum oil con- 15 taining unsaturated hydrocarbons to nondestructive hydrogenation by heating said on in a stream RALPH H. McKEE. 

